'02 wrangler rear end clunk and shift, in low gears/rpm

[schenkenator]

'02 wrangler sahara, 5spd manual, 50k miles. lifted with 33x12.5 tires

i have a shift in my rear end with a slight clunk. this typically only happens in 1st thru 3rd gear. shift into gear, release clutch and slowly step on gas while in low rpms, and the shift and clunk are the most prominent. it will still do it in higher rpm/spped but tends to be worse in lower. seems the lower gears, because of the higher torque also makes it worse. i can move my rear driveshaft just a bit, but i havnt seen any shift in my u joints. i do have a small leak in my rear axel/driveshaft connection. seal is on the way!

i have also tested this while parked, parking brake engaged, release clutch slowly step on gas but doesnt seem to shift or clunk. only while moving.

thanks in advance